Corrosion Behavior and Passive Film Characterization of Fe50Mn30Co10Cr10 Dual-Phase High-Entropy Alloy in Sulfuric Acid Solution

This study investigated the corrosion properties of a Fe50Mn30Co10Cr10 dual-phase high-entropy alloy (DP-HEA) in 0.1 M H2SO4 aqueous solution. The observed corrosion properties of the DP-HEA were compared with those of an equiatomic CoCrFeMnNi high-entropy alloy (HEA). Moreover, a passive film formed on the surface of the DP-HEA in an acidic environment was directly imaged and characterized for the first time through high-resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS). Both alloys exhibited typical active-passive behaviors in the potentiodynamic polarization test and presented similar passive current densities. The HR-TEM results revealed that the anodic passive films formed on the surfaces of the two alloys had similar thicknesses (3-5 nm). However, potentiodynamic polarization measurements showed that the DPHEA had a higher corrosion current density and lower corrosion potential than did the HEA. XPS revealed that the anodic passive film formed on the DP-HEA contained a lower ratio of Cr2O3/Cr(OH)(3), which led to poor corrosion resistance properties, as demonstrated by the potentiodynamic polarization measurements and electrochemical impedance spectroscopy. (C) 2020 The Electrochemical Society (ECS). Published on behalf of ECS by IOP Publishing Limited.